public class Mic {
    public static void main(String[]args) {
        long a = 1;
        for (int i = 1; i <= 20; i++) {

            a *= i;
          //  a = a * i;
        }
        System.out.println(a);


       /* for (int i = 1;i<10;i++){
            for (int j= 1;j <= i; j++){
                System.out.print( i + "x" + j + "=" + (i * j)+" ");
            }
            System.out.println();
        }*/
      }
    }
